I installed steam as an ovelay and it works ok. However after downloading some games,
I get an error while trying to start a game: "Unsupported video card. Your video card or it's driver may not be supported..."

I have this video card and open source radeon driver is installed in my system:

Please advise how to run the game by terminal (or any log file) so can see what are exact complains of steam?_________________“You can take our property, our sweet homes, even our cloths...
But don't touch the streets, Ah, That's NO, NO, NO!
The streets are our @world's compilable kernel ...”

You are right! OpenGL was old version: OpenGL version string: 2.1 Mesa 17.0.6
I added media-libs/mesa -bindist to package.use and after updating the system I get now:

Code:

OpenGL core profile version string: 4.1 (Core Profile) Mesa 17.0.6

At the moment it fixed the "Unsupported video card..." message however the game still does not start,
and get this error message: "An Error occurred while updating the game..."
In dmesg looks the right radeon firmware.
Here llvm - Is it latest?

game still does not start, and get this error message: "An Error occurred while updating the game..."

As always, try to run steam without steam runtime (STEAM_RUNTIME=0 steam), and forcing it over system libraries (STEAM_RUNTIME_PREFER_HOST_LIBRARIES=0 steam). If this doesn't work, from steam settings empty your download cache, verify game download, and try another download server. In order to dig deeper, you would need to provide more info about your system. To be more specific, anything unusual with security (such as hardened kernel), filesystem and network would be prime suspects. As an example, you might have 64bit NetworkManager which conflicts with the 32bit version which steam ships and requires. I have set both 64bit and 32bit ABI system wide, and my only issue is I should have done it long ago.

pmam wrote:

Here llvm - Is it latest?

Radeon 5850 should use mesa "radeon" driver instead of "radeonsi", and with radeon llvm isn't used as shader compiler. Running both mesa and llvm as stable or keyworded is just fine.

pmam wrote:

How to run the game from terminal in order to see error messages?

Default install location is ~/.local/share/Steam/Steamapps/common/the_game, just run from terminal. Most games depends on steam to be running, but some work without steam running. Many games will depend on steam runtime, and might not lauch, but some are shipped with libraries they need, and will work.

and after command ./run the game finally had started!
After "checking files and downloading..." the game has launched, however... The colors not ok, psychedelic
BTW: Why can not run the game from steam run-time ( I mean running steam from menu rather than terminal)

Quote:

anything unusual with security (such as hardened kernel), filesystem and network would be prime suspects.

EDIT: In the past War Thunder was running ok with fglrx propriety driver, but got the same issue of "The colors not ok, psychedelic" while using radeon's open source driver. At the moment fglrx is not supported by radeon and is not compatible with latest ver xorg.
May be we still have advantage of the propriety driver vs open source?

and after command ./run the game finally had started!
After "checking files and downloading..." the game has launched, however... The colors not ok, psychedelic
BTW: Why can not run the game from steam run-time ( I mean running steam from menu rather than terminal)

Good to hear that you are getting forward. Steam ships it's own runtime of really old libraries for game developers to link to, and these libraries are the issue. By launching steam you are getting a mix of system and steam's libraries, and these somehow conflict in a way that doesn't in you case let War Thunder connect to it's servers. Now that we know it works without steam runtime, we can be certain the cause isn't somewhere else.

In the past War Thunder was running ok with fglrx propriety driver, but got the same issue of "The colors not ok, psychedelic" while using radeon's open source driver. At the moment fglrx is not supported by radeon and is not compatible with latest ver xorg.
May be we still have advantage of the propriety driver vs open source?

Well, r600 is an old driver, and not many developers care about it. Also, back in the day when r600 was in active developement, they decided to use a shader compiler called sb. Person who wrote it couldn't stay around to support it, and not too many developers understand it well enough to easily fix bugs. But even sb is being worked upon, as you can see from logs:
https://cgit.freedesktop.org/mesa/mesa/log/src/gallium/drivers/r600/sb
The prop driver is abandoned. You just need to pick the lesser of two evils.

If I were in you boots, I would just setup wine with gallium-nine to play it, and cc to b.f.o #100387 linked above to get news when the bug is fixed. You might ever get better performance with gallium-nine.

By your great support, at least I know the status of current setup...
I will follow the bug process and hope for good news.
I am not familiar with gallium-nine - need to read and see how to setup.
Looks that radeon and linux do not keep on good relationship with old hardware.

For gallium-nine, you just enable USE=d3d9 for mesa and wine. If you are using masked testing ebuilds for wine, pick either wine-d3d9 or wine-any, but default wine-2.3 will work too. After that you just run winecfg, and set "Enable Gallium Nine for better D3D9 graphic performance". I think you can install steam with winetricks. I have a 5770 on an another computer, and it's still doing fine. Most games work, but not everything.